The present invention relates in general to proportional solenoid valves, and more particularly to the displacement control structure of a proportional solenoid valve through which fluid flow is precisely controlled.
The present valve is an improvement on the valve disclosed in U.S. Pat. No. 4,245,815, assigned to the assignee of the present invention.
A proportional solenoid valve allows the flow through the valve to controllably vary, whereas a standard solenoid valve is either completely open or completely closed. In prior art proportional valves, such as that shown in U.S. Pat. No. 4,245,815, a compression spring is used to provide a force opposite to that of the solenoid. When the solenoid power is off, the spring forces the armature assembly against the valve seat, and the valve is closed. As the solenoid power gradually increases, the armature assembly should move gradually away from the valve seat, allowing the flow through the valve to also gradually increase. However, a low-stiffness spring such as that shown in
U.S. Pat. No. 4,245,815, is quickly overcome by the solenoid pull force, which causes the valve to immediately open completely. Therefore, in prior art valves, additional features are required to provide the necessary stiffness to ensure proportional travel control of the armature assembly. Such prior art valves require high precision machining and costly assembly techniques.
It therefore is an object of the present invention to provide a proportional solenoid valve having a spring with the required stiffness to ensure proportional travel control of the armature assembly.
It also is an object of the present invention to provide a damper mounted on the armature assembly of a proportional solenoid valve to ensure proportional travel control of the armature assembly.
It is a further object of the present invention to provide a seal configuration in a proportional solenoid valve so that the spring that opposes the solenoid pull force is insulated from any dimensional instability of the seal or the armature assembly.